The present invention generally relates to a semiconductor device, and more specifically relates to a semiconductor device of the type having a thin film resistor, such as an analog IC. The analog IC contains as one component a high resistance circuit which can be composed of a thin film resistor. The thinner the film thickness, the higher the resistance value.
FIG. 2 is a structural sectional view of the conventional semiconductor device having a thin film resistor. A semiconductor substrate 21 is formed thereon with a MOS transistor composed of a gate electrode 22 and a pair of source and drain regions 23. An inter-layer insulating film 24 is deposited over the source and drain regions 23, and the gate electrode 22. Thereafter, a contact hole 25 is opened in the insulating film 24 to effect electrical interconnection through a patterned metal film 29. Further, another inter-layer insulating film 27 is disposed on a thin film resistor 26 which can be connected to the patterned metal film 29 through a contact hole 28 formed in the inter-layer insulating film 27.
In the conventional semiconductor device having a thin film resistor, the contact hole 25 is covered temporarily with the inter-layer insulating film 27 when the film 27 is formed over the thin film resistor 26. During the course of etching and removing of this inter-layer insulating film 27, the precedingly formed contact holes 25 are also etched to cause broadening of the diameter of the contact hole 25 and therefore variation of the contact hole diameter.
For this reason, in the semiconductor device having a thin film resistor, considerable margin is needed for design dimension around a contact hole 25, thereby hindering micronization of the device. Moreover, mask patterns designed for a regular semiconductor device having no thin film resistor cannot be utilized as it is, thereby increasing additional design work.
Further, in the conventional semiconductor device, when etching the insulating film 27 prior to formation of the patterned metal film 29 made of aluminum, there might be caused overetching, resulting in the drawback that the thin film resistor 26 is removed away.